Date: September 18th, 2019

Reference: Scheuermeyer et al. A Multicenter Randomized Trial to Evaluate a Chemical-first Cardioversion Strategy for Patients with Uncomplicated Acute Atrial Fibrillation. AEM Sept 2019

Guest Skeptic: Dr. Chris Bond is an emergency medicine physician and clinical lecturer in Calgary. He is also an avid FOAM supporter/producer through various online outlets including TheSGEM.

Case: A 55-year-old male presents to the emergency department with sudden onset of palpitations and pre-syncope starting one hour ago. He has no chest pain or shortness of breath and aside from a heart rate of 140 beats per minute, the rest of his vital signs appear within normal limits. His past medical history is significant for hypertension for which he takes perindopril. His ECG shows atrial fibrillation with a rapid ventricular response.

Background: Atrial fibrillation is the most commonly encountered significant dysrhythmia in the emergency department (1). We have covered this topic a number of times on the SGEM.

  • SGEM#88: Shock Through the Heart (Ottawa Aggressive Atrial Fibrillation Protocol)
  • SGEM#133: Just Beat It (Atrial Fibrillation) with Diltiazem or Metoprolol?
  • SGEM#222: Rhythm is Gonna Get You – Into an Atrial Fibrillation Pathway
  • SGEM#260: Quit Playing Games with My Heart – Early or Delayed Cardioversion for Recent Onset Atrial Fibrillation?

The most recent episode looked at whether late cardioversion is non-inferior to early cardioversion (SGEM#260) in acute atrial fibrillation. The SGEM bottom line from that episode was that the late approach was non-inferior to early approach and that both strategies achieve high rates of sinus rhythm at the 4-week follow up (>90%).

In uncomplicated patients with symptoms less than 48 hours and no stroke or TIA in the past six months, the 2018 Canadian Cardiovascular Society (CCS) guidelines permit rate or rhythm control (2).

There is significant variability in the management of patients with acute atrial fibrillation, with the proportion undergoing rhythm control ranging from 42-85% in Canadian academic centres (3). The rhythm control strategies typically employed are chemical cardioversion with procainamide infusion or electrical cardioversion with electrical countershock (3-6).

Both of these strategies appear safe from prior studies, but comparative effectiveness data is lacking. Thus, Canadian management varies, with 56% of patients receiving a chemical-first approach and 44% an electrical-first approach (3).

Clinical Question: In emergency department patients with atrial fibrillation, is sinus rhythm achieved more rapidly with electrical-first rhythm control when compared with chemical-first rhythm control?

Reference: Scheuermeyer et al. A Multicenter Randomized Trial to Evaluate a Chemical-first Cardioversion Strategy for Patients with Uncomplicated Acute Atrial Fibrillation. AEM Sept 2019

  • Population: Adults between 18 and 75 years of age with atrial fibrillation less than 48 hours duration and a CHADS2 score less than two.
    • Excluded: Hemodynamic instability, atrial flutter, CHADS2 score greater than or equal to two, patients with an acute underlying medical illness, recent cardiac procedure, acute intoxication or withdrawal from alcohol or illicit substances. They also excluded those who attended the emergency department for other reasons (eg. trauma, gout) who were incidentally found to be in atrial fibrillation.
  • Intervention: Chemical cardioversion with procainamide (a dose of 17mg/kg up to a maximum of 1500mg infused over one hour was recommended). This was followed by electrical cardioversion if chemical cardioversion was unsuccessful.
  • Comparison: Electrical cardioversion using a synchronized biphasic waveform sequence of 100J to 150J to 200J to a maximum of three shocks were allowed. Patients were sedated at the physicians’ discretion. The study recommended an initial propofol bolus of 0.50 mg/kg, with further slow boluses of 0.25 mg/kg every minute until adequate sedation was achieved.This was followed by chemical cardioversion with procainamide if electrical cardioversion was unsuccessful.
  • Outcome:
    • Primary Outcome: Proportion of patients discharged within four hours of emergency department arrival.
    • Secondary Outcomes: Additional median time intervals, emergency department-based adverse events, and thirty-day patient-centred outcomes.

Dr. Frank Scheuermeyer

This is an SGEMHOP episode which means we have the lead author on the show. Dr. Frank Scheuermeyer is an emergency physician researcher director at St. Paul’s Hospital in Vancouver, BC. He is also the associate director of research for the University of British Columbia Department of Emergency Medicine, and the Cardiovascular Emergencies lead for the British Columbia Emergency Medicine Network.

Authors’ Conclusions: In uncomplicated ED AF patients, chemical-first and electrical-first strategies both appear to be successful and well tolerated; however, an electrical-first strategy results in a significantly shorter ED length of stay. Our results should encourage clinicians to initially consider an electrical-first approach for such patients.”

Quality Checklist for Randomized Clinical Trials:

  1. The study population included or focused on those in the emergency department. Yes
  2. The study participants were adequately randomized. Yes
  3. The randomization process was concealed. Yes
  4. The participants were analyzed in the groups to which they were randomized. Yes
  5. The study participants were recruited consecutively (i.e. no selection bias). No
  6. The participants in both groups were similar with respect to prognostic factors. Yes
  7. All participants were unaware of group allocation. No
  8. All groups were treated equally except for the intervention. Yes
  9. Follow-up was complete (i.e. at least 80% for both groups). Yes
  10. All patient-important outcomes were considered. Yes
  11. The treatment effect was large enough and precise enough to be clinically significant. Yes

Key Results: Overall, 222 eligible patients were screened and 84 were ultimately enrolled and randomized (41 chemical-first and 43 electrical-first). The median age was in the late 50’s, more than a third were female and three-quarters had a history of atrial fibrillation.

1/3 of patients were discharged in four hours with chemical-first group compared to 2/3 in the electrical-first group.

  • Primary Outcome: Proportion of patients discharged within four hours of emergency department arrival.
    • In the chemical-first group, 13 of 41 (32%) were discharged within four hours, compared with 29 of 43 (67%) in the electrical-first group. Difference 36% (95% CI 16-56%, P<0.001) for a number needed to treat of 3.
  • Secondary Outcomes: Additional median time intervals, emergency department-based adverse events and thirty-day patient-centred outcomes.
  • Adverse Events:
    • Chemical-first group had 10 adverse events (24%) and electrical group had 11 (26%). All had minimal-risk outcomes.
    • There were no strokes or deaths in either group at 30 days.
    • Quality of life scores at 3 and 30 days were similar for both groups across all domains.

You can listen to the podcast on iTunes or Google Play to hear Frank’s answers to our five nerdy questions.

1) Consecutive Patients – You did not have consecutive recruitment of patients. Recruitment depended on whether or not a research assistant was available. That often means no nights, weekends or holidays. This could have introduced some selection bias. How do you think this may have impacted your results? (note it was only 8/135 eligible patients)

2) More than an ECG – For this study, you encouraged physicians to obtain an ECG, complete blood count, electrolytes, creatinine, TSH, troponin and chest x-ray on all patients. Do you recommend this in practice, and with high sensitivity troponins, wouldn’t you obtain many intermediate elevations from the tachycardia if it was prolonged?

3) Exclusion – You excluded patients over the age of 75. My good friend and geriatric emergency medicine guru Dr. Chris Carpenter may accuse you of practicing ageism. Why did you exclude these older patients?

4) Outcomes – One outcome we found interesting was the emergency department re-visits at 3 and 30 days. The numbers were not statistically significant, but for chemical vs. electrical cardioversion they were 5 vs. 1 at 3 days and 9 vs. 3 at 30 days. Is there any literature to support a difference in recurrence rate for the two methods?

Speaking of outcomes, you changed your primary outcome. Originally you had emergency department length of stay. This was then changed to the proportion of patients discharged within four hours of emergency department arrival. Can you explain why you made this change?

5) External Validity – I absolutely love this study as an emergency medicine practitioner in Calgary. We are about as pro-electricity as you can get. Why do you think there is such variation in use of electrical vs. chemical first cardioversion across Canada and worldwide?

I also really liked that your study sites ranged from big tertiary referral centres like with all the resources, to small community hospitals where I work with no on-site cardiologist. This really strengthens the external validity to different Canadian emergency departments. However, do you think this trial has external validity to other countries like the USA, Australia and European countries different practice environments?

Comment on Authors’ Conclusion Compared to SGEM Conclusion: We agree with the authors conclusions.

SGEM Bottom Line: Consider implementing an electrical-first rhythm control strategy for low risk patients with atrial fibrillation.

Case Resolution: After a discussion with your patient, you make a shared decision to perform synchronized cardioversion as an electrical-first rhythm control strategy.

Clinical Application: This study provides support for an electrical-first rhythm control strategy in patients with uncomplicated atrial fibrillation to reduce emergency department length of stay.

Dr. Chris Bond

What Do I Tell My Patient? Your heart is in an abnormal rhythm called atrial fibrillation and is going too fast. This is why you are feeling lightheaded and like your heart is racing. We have several safe methods to get you out of this rhythm, which include making you sleepy and giving your heart some electricity or giving you intravenous medication. The electrical method is more effective on the first attempt and will generally result in you going home 1-2 hours sooner than the intravenous medication. For the electricity method, we will give you an anesthetic that will make you forget the procedure in most cases. If one method doesn’t work, then we generally try the other method afterward.

Keener Kontest: Last weeks’ winner was Dr. Trevor Slezak a PGY4 EM resident from WashU. He found that there were 24 Nobel Laureates who had done research at Washington University in St. Louis.

Listen to the podcast to hear this weeks’ trivia question. If you know the answer, send an email to with “keener” in the subject line. The first correct answer will receive a cool skeptical prize.

SGEMHOP: Now it is your turn SGEMers. What do you think of this episode on rhythm control in atrial fibrillation? Tweet your comments using #SGEMHOP. What questions do you have for Frank and his team? Ask them on the SGEM blog. The best social media feedback will be published in AEM.

Also, don’t forget those of you who are subscribers to Academic Emergency Medicine can head over to the AEM home page to get CME credit for this podcast and article. We will put the process on the SGEM blog:

  • Go to the Wiley Health Learning website
  • Register and create a log in
  • Search for Academic Emergency Medicine – “September”
  • Complete the five questions and submit your answers
  • Please email Corey ( with any questions or difficulties.

Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine.


  1. Naccarelli GV, Varker H, Lin J, Schulman KL. Increasing prevalence of atrial fibrillation and flutter in the United States. Am J Cardiol 2009;104:1534–39.
  2. Stiell IG, Macle L; CCS Atrial Fibrillation Guidelines Committee. Canadian Cardiovascular Society atrial fibrillation guidelines 2010: management of recent-onset atrial fibrillation and flutter in the emergency department. Can J Cardiol 2011;27:38–46.
  3. Stiell IG, Clement CM, Brison RJ, Rowe BH, Borgund- vaag B, Langhan T. Variation in management of recent-onset atrial fibrillation and flutter among academic emergency departments. Ann Emerg Med 2011;57:13–21.
  4. Michael JA, Stiell IG, Agarwal S, Mandavia DP. Cardioversion of paroxysmal atrial fibrillation in the emer- gency department. Ann Emerg Med 1999;33:379–87.
  5. Stiell IG, Clement CM, Symington C, Perry JJ, Vaillancourt C, Wells G. Emergency department use of intra-venous procainamide for patients with acute atrial fibrillation or flutter. Acad Emerg Med 2007;14:1158–64.
  6. Stiell IG, Clement CM, Perry JJ, et al. Association of the Ottawa Aggressive Protocol with rapid discharge of emergency department patients with recent-onset atrial fibrillation or flutter. CJEM 2010;12:181–91.